Patent Application
20130252185
The invention relates generally to furnaces having igniter elements and, more particularly, to furnaces having shields for the igniter elements.
In furnace applications, igniters commonly include an igniter element. The igniter is positioned such that the “hot spot” of the igniter element, or the portion of the igniter element that reaches the hottest temperature, is placed directly in the mixture of fuel and air to create the point of ignition. If the igniter is not at a temperature hot enough to cause the fuel and air mixture to combust, the fuel flow to the furnace will automatically shut off. A predominant cause of igniter element cooling is secondary combustion airflow. Secondary combustion airflow moves quickly past the igniter causing the igniter element to cool to a temperature below that required to ignite the surrounding fuel. Systems using less power are also susceptible to igniter element cooling because less power is used to heat the igniter. Some furnace applications require the furnace to use a lower voltage power supply, such as 98V for example, rather than the typical 110V; therefore less power is applied towards heating the igniter than in a full voltage system. If the igniter is too cool to ignite the fuel and air mixture, no heat will be produced from the furnace.
According to an exemplary embodiment of the invention, a burner assembly for use in a gas appliance is provided including a top plate configured to form the geometric top half of at least one burner and a bottom plate configured to form the geometric bottom half of at least one burner. The top plate and the bottom plate are joined together to form a burner and a burner carryover. An igniter air shield extends from either the top plate or the bottom plate such that the igniter air shield diverts secondary combustion air flowing around the burner.
According to another embodiment of the invention, a burner unit is provided including a burner assembly having a plurality of axially aligned burners. The burner unit also includes a burner box for receiving the burner assembly. An igniter assembly is mounted such that the igniter element is adjacent the burner assembly. The igniter assembly includes an igniter element extending from an insulative body. An igniter air shield extends from a portion of the burner assembly such that the igniter air shield diverts secondary air flowing around the burner assembly away from the igniter element.
According to yet another embodiment of the invention, a furnace is provided including a burner assembly having a plurality of axially aligned burners. A burner box receivers the burner assembly. An igniter assembly includes an igniter element connected to an insulative body. The igniter assembly is mounted such that the igniter element is adjacent the burner assembly. An igniter air shield, extending from the burner assembly, diverts secondary air flowing around the burner assembly away from the igniter element.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
Burner assembly 14 is mounted within burner box 12 and is supplied with combustion air. As will be discussed in more detail below, the burner assembly 14 includes a gas manifold 36 with a gas orifice 38 (see
Air from the space to be heated is drawn into furnace 10 by blower 52, which is driven by blower motor 54 in response to control signals that are generated by furnace control 50. The discharge air from the blower 52, herein called circulating air, passes over the heat exchanger assembly 20 before being directed to the space to be heated through a duct system (not shown).
Referring now to
The burner assembly 14 includes a plurality of parallel and equidistant burners 130. In the exemplary embodiment portrayed in the FIGS., the burner assembly 14 includes four burners 130. However, the burner assembly 14 may include any number of burners 130. In an exemplary embodiment, the plurality of burners 130 is formed from two stamped flat metal plates, a top plate 120 and a bottom plate 122. The top plate 120 and the bottom plate 122 of the burner assembly 14 are stamped so that the top plate 120 contains the geometry of the upper half of each burner and the bottom plate 122 contains the geometry of the lower half of each burner. Disposed between each burner half is at least one burner carryover 147 to assist in the ignition process. The plates 120, 122 thus divide the burners 130 and burner carryovers 147 symmetrically along the central axis Z of each burner 130 so that when the plates 120, 122 are assembled in face to face contact, the overall shape of each burner 130 is produced. Top and bottom plates 120, 122 may be fastened together by any suitable means so that the opposed flat surfaces of the plates 120,122 are held in close intimate contact along the length and breadth of the plates. Joining the top plate 120 and the bottom plate 122 creates a horizontal plane extending through the entire burner assembly 14 and through the center of each of the plurality of burners 130 and burner carryovers 147.
Each burner 130 within the burner assembly 14 has a fuel port 132 at a first end of the burner 130. The fuel port 132 is a cylindrical element that aligns a burner 130 with a respective fuel supply to direct pressurized fuel into the burner 130. The fuel port 132 of each burner 130 is positioned adjacent to and in axial alignment with a tubular nozzle 138. Each nozzle 138 has a flared inlet end 134 and a cylindrical outlet end 140. A flame retainer housing 142 is integrally joined to the outlet end 140 of the tubular nozzle 138 and contains a generally cylindrical flame retainer 144. The flared inlet end 134 has a larger diameter inlet opening than the fuel inlet opening defined by the fuel port 132. An opening 146 is stamped into each of the plates 120, 122 between the fuel port 132 and the inlet 134 to the tubular nozzle 138. Each opening 146 is sufficiently large so that an unimpeded airflow will be available to support the combustion when the burner is operating at capacity. The burner carryovers 147 are sized to sufficiently carry the flame to the exit of each flame retainer 144 during the ignition process.
A support piece 150 extends perpendicularly from the top surface 110 towards the bottom surface 112 of the burner box 12. Fastened to this support piece 150 is an igniter mounting structure 152 having a hole in which an igniter assembly 160 is inserted. The support piece 150 and the igniter mounting structure 152 are positioned such that the mounted igniter assembly 160 is adjacent an outlet 140 of a burner 130 located at an end of the burner assembly 14. The igniter assembly 160 includes an insulative body 162 and an igniter element 164 extending from within the insulative body 162. The igniter element 164 is arranged to provide a hot surface to the outlet section of the burner carryover 147 at start up. The igniter element will ignite the primary air/fuel mixture moving through the burner 130 and burner carryover 147 and propagate the flame to the exit of each flame retainer 144.
As the fuel is injected through the fuel port 132, air also enters the burner 130 due to the difference of the diameter of the inlet and the diameter of the fuel port 132. The fuel and air combine at the inlet 134 of the tubular nozzle 138 to create a primary fuel/air mixture. As the primary fuel/air mixture flows through the burner 130 and the burner carryover 147, the primary fuel/air mixture contacts the hot surface igniter element 164 causing the mixture to ignite at the burner carryover 147 closest to the igniter element 164. The flame is then carried across each burner carryover 147 and the exit of each flame retainer 144. Secondary combustion air (See
Referring now to
The igniter air shield 170 may be formed integrally with the burner assembly 14. In an exemplary embodiment, if the burner assembly 14 includes a stamped metal top and bottom plate 120, 122, the igniter air shield 170 may be formed as part of either the top or bottom plate 120, 122. To form the igniter air shield 170 as part of the bottom plate 122, for example, the stamped metal will include an additional area extending beyond the edge forming the outlet 140 of each burner 130. The dimensions of the area forming the igniter air shield 170 must be sufficient to create a non-turbulent flow or stable flow adjacent the outlet of the burner carryover 147 closest to the igniter element 164, and the igniter element 164. The area forming the igniter air shield 170 is then bent so that a portion of the igniter air shield 170 will extend into secondary combustion air flow B around the bottom plate 122 to divert it away from the igniter element 164. The angle of the bend of the igniter air shield 170 may range from zero to ninety degrees from the horizontal plane of the plate. In an alternate embodiment, the igniter air shield 170 may be a separate part that is then attached to the portion of the burner assembly 14 adjacent the burner carryover 147 closest to the igniter element 164. The igniter air shield 170 may be attached by welding, fastening, or any other suitable means. Additionally, a second igniter air shield 170 may extend from the top of the burner assembly 14 adjacent the igniter element 164 to divert the secondary air flow represented by arrow A away from the igniter element 164.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/613,735 filed Mar. 21, 2012, the contents of which are incorporated herein by reference thereto.
| Number | Date | Country | |
|---|---|---|---|
| 61613735 | Mar 2012 | US |
